re PR c++/84662 (internal compiler error: tree check: expected class 'type', have...

re PR c++/84662 (internal compiler error: tree check: expected class 'type', have 'exceptional' (error_mark) in is_bitfield_expr_with_lowered_type, at cp/typeck.c:1944)

	PR c++/84662
	* pt.c (tsubst_copy_and_build) <case TEMPLATE_ID_EXPR>: Use
	RETURN instead of return.
	<case POINTER_PLUS_EXPR>: Likewise.
	<case CONVERT_EXPR>: If op0 is error_mark_node, just return
	it instead of wrapping it into CONVERT_EXPR.

	* g++.dg/cpp1y/pr84662.C: New test.

From-SVN: r258146